1. Field of the Invention
This invention relates to an equipment of semiconductor fabrication, and more particularly to an equipment for forming a glue layer over an opening in order to round an upper corner of the opening.
2. Description of Related Art
Currently, semiconductor devices are widely involved in many products and services in our daily life. All these semiconductor devices are fabricated on a wafer through many processes, such as photolithography, deposition, ion implantation, or etching, to form an integrated circuit (IC) device. One wafer usually includes a large number of IC devices.
In semiconductor fabrication on a wafer, or called a substrate, an opening with high aspect ratio, which is defined as a ratio of the depth to the width, is needed in some situations. The opening, such as a via opening or a contact opening, is formed in a dielectric layer and is filled with a metallic material, such as tungsten, to form a metal plug. The dielectric layer is usually sandwiched between two metal layers or between one metal layer on the top and the substrate on the bottom. The purpose of the metal plug is to interconnect these two metal layers for an interconnection between device elements. Since the material properties of the metal plug and the dielectric layer are different, there usually is a poor adhesion between them at the sidewall of the opening. In order to improve the adhesion between the metal plug and the dielectric layer, a conformal glue layer, or called barrier layer, is usually formed over the opening before the metal plug is filled into the opening. The glue layer can improve adhesion of the metal plug in the dielectric layer.
Currently, the glue layer typically includes a mix layer of titanium and titanium nitride as shown in FIG. 1A and FIG. 1B, which are cross-sectional views, illustrating a fabrication process of an conventional opening plug. In FIG. 1A, a dielectric layer 102 is formed on a substrate 100. An opening 104 is formed in the dielectric layer 102. A titanium layer 106 is formed over the substrate 100 by physical vapor deposition (PVD) and a titanium nitride layer 108 is formed over the titanium layer 106 by chemical vapor deposition (CVD). The titanium layer 106 and the titanium nitride layer 108 form together as a glue layer, which is conformal to the substrate 100. Since a high integration IC device is desired, the aspect ratio of the opening is usually high, which degrades the step coverage performance. The titanium layer 106 formed by PVD may have an overhang 106a at each upper corner 102a of the opening 104.
In FIG. 1B, a tungsten metal layer 110 is formed over the substrate 100 to fill the opening 104 of FIG. 1A. Since the existence of the overhang 106a, the step coverage performance is also poor. A void 112 is formed within the opening 104. The void 112 can induce some problems, such as current leakage, and cause a failure of the device.
The fabrication processes described above are performed in a fabrication equipment. FIG. 2 is a schematic drawing of a conventional fabrication equipment for metallization process. In FIG. 2, the substrate (not shown) is put in a load/unload chamber 202. The substrate, sequentially following the arrow direction 204, is put in a degas chamber 206 to remove remaining water vapor on the substrate, in a sputtering chamber 208 to form the opening, in a PVD chamber 210 to deposit the titanium layer 106 of FIG. 1B, and in a CVD chamber 212 to deposit the titanium layer 108 of FIG. 1B.
In this conventional fabrication equipment, there is no chamber for removing the overhang 106a of FIG. 1B. If the overhang 106 is not removed, the step coverage performance on the opening 104 is then not improved.